It is known to machine bores with an extremely high accuracy of size using arbor or mandrel honing. Examples are the machining of very small bores for car injection systems, the machining of bores in hydraulic components and the machining of the large and small offices in connecting rods.
In the case of arbor honing the honing tool set to the final diameter is moved at high rotation speed, but low stroke speed at least once and at the most three times through the bore. As a result of the high circumferential speed of the honing tool compared with the stroke speed, the honing angle during arbor honing is very small.
The problem of the invention is to further develop a honing method, whilst retaining the advantages obtained by arbor honing, with regards to a tribologically favourable surface topography.
Whereas during normal arbor honing using an arbor honing tool, the bore is only slowly traversed with a high rotational speed, the invention proposes that the arbor honing tool be at least partly used in a manner not conventional in the case of arbor honing. With a small allowance for the bore to be machined, e.g. the first stroke with the arbor honing tool can be run through with an increased stroke speed to rotational speed ratio, i.e. in other words very rapidly.
If said allowance is not as small, e.g. the first stroke, i.e. the first passage through the bore can take place at the normal speed and subsequently the tool can be rapidly retracted. Under the indicated conditions, this can also lead to the production of a cross-structure.
However, according to a further development, the bore is initially machined in the conventional manner with a stroke and a return stroke and only then is the arbor honing tool used in the unconventional manner.
Thus, the bore to be machined is machined in the same way as hitherto. Use is made of an arbor honing tool, which is moved through the bore in at least one stroke and a return stroke at a high rotational speed, but low stroke speed. Subsequently either the circumferential speed is modified or the stroke speed increased. Then, using the same tool, the bore is machined again, but now as a result of the higher stroke speed compared with the rotational speed, there is a larger angle of the honing tracks. On retraction it can be ensured that a cross-structure is obtained, which then leads to the desired, improved tribological characteristics.
As a result of the characteristics of an arbor honing tool, which undergoes stress relief, the possibility arises during the return stroke that the abrasion is deeper than the honing tracks of the forward stroke. In certain circumstances this can lead to a risk of no cross-structure being formed. In order to obviate this risk in all cases, according to a further development of the invention the tool is reset prior to the remachining return stroke and is consequently stress-relieved. This resetting or stress relief can take place to such an extent that the honing tracks occurring during the return stroke have the same depth as those formed during the forward stroke.
However, it is also possible and is proposed by the invention, to perform remachining with several and in particular rapid strokes, so that as a result of the plurality of strokes there are cross-structures having the same depth.
A further infeeding of the tool is possible, so as to reliably cover the previously formed tracks.
It is also possible during the downward stroke to make the abrasion so small that in the case of a fixed set tool during the upward stroke not all the tracks of the downward stroke are abraded.
According to a further development of the invention, following onto remachining a further remachining takes place, in which the peaks of the surface structure are smoothed. This constitutes a type of plateau machining in order to be able to produce a specific support structure.
According to the invention, the same tool as for the preceding remachining can be used for said smoothing.
However, it is also possible and is proposed by the invention that the smoothing of the peaks can take place with the aid of another tool by means of arbor honing or normal honing.